The long-awaited MTA Subway Time app went live shortly after 9 this morning for passengers with iPhones and iPod Touch devices. The MTA had planned versions for Android and Windows users, but said Friday that third-party developers will build apps on those platforms instead. A web version also launched on Friday.

For now Subway Time only provides minutes-to-arrival times for trains on the Nos. 1, 2, 3 and 4, 5, 6 lines, along with the 42nd Street Shuttle, known internally as the “A Division.” The agency will look to third-party developers to make it more productive.

According to the MTA, the data feed coming from the rail control center for the A Division (1,2,3,4,5,6 and 42nd Street Shuttle) sends an update every 30 seconds on the location of every train on those lines. That information feeds the countdown clocks, which use an algorithm to estimate the arrival time at a particular station. The app is designed to receive the same arrival estimates as the countdown clocks on station platforms.